Union officials have accused hotels of breaking the law on how many hours staff may work since the introduction of the Working Time Directive last October.
The Transport and General Workers' Union (TGWU) says that some staff at Radisson Edwardian are working more than 48 hours a week without being aware they must sign an opt-out clause to do so.
But Roy Gooder, manager of human resources at Radisson Edwardian, insisted that staff had been made aware of the changes and that only 25 of the group's 1,500 staff had opted out of its introduction of a 40-hour week.
Those required to work longer hours had been contacted individually, and Gooder said he was keen to talk to anyone who felt they had not been properly informed of their rights.
Dave Turnbull, London district officer for the union, added that some Park Lane hotels were blacklisting casual banqueting staff who chose not to sign away their rights to shorter working hours.
Turnbull said that many restaurant workers were still not being paid for the hours they had to linger for the last customers to leave, while staff choosing not to work on bank holidays were being forced to take the days from their three-week annual entitlement.
James Tynan, hotel manager at the Grosvenor House, said he was unaware of any blacklisting and would be "horrified" if it was happening. About 50% of staff have opted out of the limit, and Tynan said the percentage was high among older, loyal casual staff whose services the hotel was eager to retain.
He added that younger casuals with families and mortgages were keen to work longer.
Turnbull said that the directive was riddled with loopholes that unscrupulous employers continued to exploit. And he feared that, as long as hospitality staff needed to work long hours to make a living wage, they would not be able to afford the luxury of opting out - a situation which the advent of the national minimum wage next month would do little to alter. by Angela Frewin